Field of the Invention
The present invention relates to a solid electrolytic capacitor element, a solid electrolytic capacitor, a method for producing a solid electrolytic capacitor element, and a method for producing a solid electrolytic capacitor.
Description of the Related Art
A solid electrolytic capacitor includes, for example, a solid electrolytic capacitor element prepared by forming an oxide coating film that constitutes a dielectric layer on a roughened surface of a valve metal substrate, forming a masking layer to separate an anode portion and a cathode portion from each other, and sequentially forming, on the dielectric layer outside the anode portion, a solid electrolyte layer, and a carbon paste layer and a silver paste layer that constitute a current collector layer as described in Japanese Unexamined Patent Application Publication No. 2009-158692, for example.
However, typical solid electrolytic capacitors such as one disclosed in Japanese Unexamined Patent Application Publication No. 2009-158692 sometimes have an issue of large leak current.
FIGS. 7A and 7B are schematic cross-sectional views of an example of a solid electrolytic capacitor element included in a typical solid electrolytic capacitor.
A solid electrolyte layer 40 and a current collector layer 50 constituting a typical solid electrolytic capacitor element 6 are typically each prepared by immersing one end portion of a valve metal substrate 10, where a cathode portion will be formed, in a raw material solution or dispersion of a conductive polymer, carbon paste, or the like.
However, when the valve metal substrate 10 is immersed in the raw material solution or dispersion of a conductive polymer for forming a solid electrolyte layer 40, a masking layer 35 repels the raw material solution or dispersion. As illustrated in FIG. 7A, this sometimes results in formation of a gap between the masking layer 35 and the solid electrolyte layer 40.
When carbon paste or the like is applied to the solid electrolyte layer 40 under such conditions so as to form a current collector layer 50, carbon paste penetrates the gap, and, as illustrated in FIG. 7B, the current collector layer 50 comes into contact with a dielectric layer 20. It is considered that the leak current will increase as a result.